Browsing by Author "Chiang, Chao-Cheng"

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2-Alkyl-5-thienyl-Substituted Benzo[1,2-b:4,5-b ']dithiophene-Based Donor Molecules for Solution-Processed Organic Solar Cells
(2013-10-09)
Patra, Dhananjaya
;
Huang, Tzu-Yen
;
Chiang, Chao-Cheng
;
Maturana, Ramon Orlando Valencia
;
Pao, Chun-Wei
In this study, we have strategically designed and convergently synthesized two novel, symmetrical, and linear A-D-A-type pi-conjugated donor molecules (TBDTCNR, TBDTCN), each containing a planar electron-rich 2-octylthiene-5-yl-substituted benzodithiophene (TBDT) unit as the core, flanked by octylthiophene units and end-capped with electron-deficient cyanoacetate (CNR) or dicyanovinyl (CN) units. We thoroughly characterized both of these materials and investigated the effects of the end groups (CNR, CN) on their optical, electrochemical, morphological, and photovoltaic properties. We then fabricated solution-processed bulk heterojunction organic solar cells incorporating TBDTCNR and TBDTCN. Among our tested devices, the one containing TBDTCNR and [6,6]-phenyl-C-61-butyric acid methyl ester in a 1:0.40 ratio (w/w) exhibited the highest power conversion efficiency (5.42%) with a short-circuit current density (J(sc)) of 9.08 mA cm(-2), an open circuit voltage (V-oc) of 0.90 V, and an impressive fill factor (FF) of 0.66 under AM 1.5G irradiation (100 mW cm(-2)). The FFs of these solution-processed small-molecule organic solar cells (SMOSCs) are outstanding when compared with those recently reported for benzodithiophene (BDT)-based SMOSCs, because of the high crystallinity and excellent stacking properties of the TBDT-based compounds.
Solution-processed benzotrithiophene-based donor molecules for efficient bulk heterojunction solar cells
(2013)
Patra, Dhananjaya
;
Chiang, Chao-Cheng
;
Chen, Wei-An
;
Wei, Kung-Hwa
;
Wu, Meng-Chyi
In this study we used convergent syntheses to prepare two novel acceptor-donor-acceptor (A-D-A) small molecules (BT4OT, BT6OT), each containing an electron-rich benzotrithiophene (BT) unit as the core, flanked by octylthiophene units, and end-capped with electron-deficient cyanoacetate units. The number of octylthiophene units affected the optical, electrochemical, morphological, and photovoltaic properties of BT4OT and BT6OT. Moreover, BT4OT and BT6OT possess low-energy highest occupied molecular orbitals (HOMOs), providing them with good air stability and their bulk heterojunction (BHJ) photovoltaic devices with high open-circuit voltages (V-oc). A solar cell device containing BT6OT and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) in a 1 : 0.75 ratio (w/w) exhibited a power conversion efficiency (PCE) of 3.61% with a short-circuit current density (J(sc)) of 7.39 mA cm(-2), a value of V-oc of 0.88 V, and a fill factor (FF) of 56.9%. After adding 0.25 vol% of 1-chloronaphthalene (CN) as a processing additive during the formation of the blend film of BT6OT: PC71BM (1 : 0.75, w/w), the PCE increased significantly to 5.05% with values of J(sc) of 9.94 mA cm(-2), V-oc of 0.86 V, and FF of 59.1% as a result of suppressed nanophase molecular aggregation.